Prior Art Statement
Single extraction of unreacted hydrocarbons from petroleum sulfonates is well-known in the art, for example, U.S. Pat. Nos. 3,493,048 and 3,504,744. Re. 22,548 to Brandt uses water to cause the separation of aqueous sulfuric and sulfonic acids and then uses sodium chloride to extract these acids from organic sulfonic acids. Thereafter, the organic sulfonic acids are neutralized. Brandt also discloses the use of solvents such as ethyl alcohol, dioxane, acetone, etc., in the extraction process.
Gale, et al in U.S. Pat. No. 3,653,437 teaches a single solvent process for the removal of unreacted oils from neutralized petroleum sulfonate surfactant mixtures. Isopropyl alcohol is the preferred solvent of Gale's process. The art also discloses the extraction of unreacted hydrocarbons from petroleum sulfonates either prior to or after the neutralization of the sulfonates, e.g., U.S. Pat. No. 4,144,266. Extraction solvents of water, alcohol, low molecular weight hydrocarbons or mixtures of these are generally preferred.
However, the single extractions of unreacted oil taught by the prior art are incomplete in that over a period of several weeks additional unreacted oil, residual raffinate, of up to about 4 percent will separate from the sulfonate product. The presence of this unreacted oil adversely affects the filterability of a slug containing the sulfonate, e.g., a micellar dispersion, which is used in an oil recovery process.
It is an object of the present invention to effect a complete separation of free unreacted hydrocarbon and residual raffinate from the sulfonate by a two step separation process. Not only does this improve the filterability of a slug containing the sulfonate which is used in an oil recovery process and result in a savings through the recovery of valuable oil, but as a result of the incomplete initial separation of the present process, additional savings are realized through a decrease in settling times and size of settling tanks normally required for a two step separation.